There is a need in the television broadcasting field to test the frequency response of video circuits and systems. One frequently used method is to apply a video sweep signal to the input of the equipment being tested and observe the resulting output signal with an oscilloscope. This procedure cannot be used with equipment that requires the presence of synchronizing pulses, however. Another widely used method is to employ a multiburst signal generator--one that produces blanking pulses upon which sync pulses and various discrete bursts of video frequencies are superimposed. The multiburst signal, which for the NTSC color television system suitably includes a series of equal-amplitude bursts of sine wave signals ranging from 0.5 MHz to 4.2 MHz plus "black" and "white" reference levels, is applied to the input of the circuit or system under test. By observing the resultant output with an oscilloscope, the frequency response of the equipment may be determined visually based on how the different frequency bursts are affected.
One of the critical areas of frequency response for NTSC color television systems is the range of frequencies between the chrominance subcarrier (3.58 MHz) and intercarrier sound (4.5 MHz). Video circuitry must be carefully adjusted so that the video signal does not interfere with the sound signal. With prior art multiburst signal generators, this is done by observing the effect of equipment adjustments on the 4.2 MHz burst and estimating the resulting cut-off frequency of the video equipment. An improved, more accurate means for determining the frequency response characteristics of video equipment within a selected range, such that between the color subcarrier and intercarrier sound frequencies, is clearly desirable.